Trichobilharzia regenti - neuropathogenic fluke
T. regenti is a neuropathogenic bird schistosome which has been discovered and described as a new species by our team in 1998. In addition to birds, the infectious larvae proved to penetrate also the skin of mammals and, therefore, T. regenti (neuro)pathogenicity is intensively investigated.
Miracidia hatch directly in the nasal tissue. They leave the eggs, waiting for contact of the duck bill with water. Then, they escape, searching for intermediate snail hosts in water bodies.
T. regenti schistosomula migrate through the duck central nervous system; after penetration of peripheral nerves (Fig.1) they start in the spinal cord and continue to the duck brain. Also in experimental mammals, they can reach the spinal cord. Parasites feed on the nervous tissue granules which are visible in the worm intestine (Fig.2) and serve probably as source of nutrients. Schistosomula of T. regenti express several isoforms of cathepsin B-like cysteine peptidases. The peptidases are localized exclusively in the gut of schistosomula (Fig.3). Unlike human schistosomes, the recombinant peptidases are inefficient against hemoglobin, but they degrade myelin basic protein. This shows parasite adaptation for migration through the nervous tissue. Adult parasites live intra- and/or extravascularly in the soft nasal tissues of ducks. They lay eggs and cause petechiae in the nasal mucosa.
Cercariae of T. regenti develop asexually within snail intermediate hosts. Then, mature cercariae escape via penetration of snail surface epithelia.